> data Vect : Nat -> Type -> Type where
>      Nil : Vect Z a
>      (::) : a -> Vect k a -> Vect (S k) a

> %name Vect xs, ys, zs

> dupAll : Vect n a -> Vect n (a, a)
> dupAll xs = zipHere xs xs
>   where
>     zipHere : forall n . Vect n a -> Vect n b -> Vect n (a, b)
